Method for producing piezoelectric actuator and method for producing liquid transport apparatus

ABSTRACT

A vibration layer is formed by the AD method on a cavity plate before forming pressure chambers, a common electrode is formed on the vibration layer, and a piezoelectric layer is formed on the common electrode by the AD method. Subsequently, the pressure chambers are formed in the cavity plate by the etching. After that, individual electrodes are formed on the piezoelectric layer. Subsequently, the stack of the cavity plate, the vibration layer, the common electrode, the piezoelectric layer, and the individual electrodes is heated at about 850° C. to simultaneously perform the annealing of the piezoelectric layer and the sintering of the individual electrodes and the common electrode. Accordingly, the atoms of the cavity plate are suppressed from being diffused into the driving portions of the piezoelectric layer.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2008-020567, filed on Jan. 31, 2008, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method for producing a piezoelectricactuator which includes a piezoelectric layer, and a method forproducing a liquid transport apparatus which includes such apiezoelectric actuator.

Description of the Related Art

In relation to an ink-jet head described in Japanese Patent ApplicationLaid-open No. 2006-54442, a piezoelectric actuator, which applies thepressure to the ink contained in a pressure chamber, is produced inaccordance with the following procedure. At first, a vibration plate,which is composed of, for example, a stainless steel material, is joinedto an upper surface of a channel unit to cover the pressure chambertherewith. A lower electrode, which serves as a diffusion-preventivelayer (diffusion barrier layer), is formed on an upper surface of thevibration plate. A piezoelectric layer is formed thereon by means of theaerosol deposition method (AD method). Further, the annealing, in whichthe piezoelectric layer is heated at a high temperature, is performed inorder that the piezoelectric layer, which is formed by the AD method,has the piezoelectric characteristic. During this procedure,constitutive atoms of the vibration plate, which are heated togetherwith the piezoelectric layer, are diffused. However, the diffusion ofthe atoms is stopped at the lower electrode which serves as thediffusion-preventive layer. The constitutive atoms of the vibrationplate are prevented from being diffused into the piezoelectric layer.Accordingly, the deterioration of the piezoelectric characteristic ofthe piezoelectric layer, which would be otherwise caused by thediffusion of the constitutive atoms of the vibration plate into thepiezoelectric layer, is suppressed.

In the case of the piezoelectric actuator described in Japanese PatentApplication Laid-open No. 2006-54442, the pressure is applied to the inkcontained in the pressure chamber by deforming the portion (activeportion) of the piezoelectric layer opposed to the pressure chamber.Therefore, the piezoelectric characteristic of the portion of thepiezoelectric layer opposed to the pressure chamber affects the drivingof the piezoelectric actuator. However, in the case of the ink-jet headdescribed in Japanese Patent Application Laid-open No. 2006-54442, thevibration plate, which is composed of, for example, the stainless steelmaterial, is arranged at the portion of the piezoelectric layer opposedto the pressure chamber. Therefore, even when the lower electrode, whichserves as the diffusion-preventive layer, is arranged between thepiezoelectric layer and the vibration plate, the lower electrode cannotsufficiently stop the diffusion of the constitutive atoms of thevibration plate. Therefore, the constitutive atoms of the vibrationplate pass through the lower electrode, the constitutive atoms arediffused into the portion of the piezoelectric layer opposed to thepressure chamber, and the piezoelectric characteristic of the concerningportion of the piezoelectric layer is deteriorated. As a result, it isfeared that the amounts of deformation of the piezoelectric layer andthe vibration plate may be lowered when the piezoelectric actuator isdriven.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for producinga piezoelectric actuator which makes it possible to maximally suppressthe decrease in the amounts of deformation of a piezoelectric layer anda vibration layer, and a method for producing a liquid transportapparatus which has such a piezoelectric actuator.

According to a first aspect of the present invention, there is provideda method for producing a piezoelectric actuator, including:

providing a base member;

forming a vibration layer with a ceramics material on a surface of thebase member;

forming a piezoelectric layer on a surface, of the vibration layer, notfacing the base member;

removing a part of the base member after forming the piezoelectric layerto form a through-hole via which the vibration layer is exposed;

forming an electrode at a portion of the piezoelectric layer to beoverlapped with the through-hole; and

annealing the piezoelectric layer after forming the through-hole. Thebase member may be formed of metal or silicon.

In the piezoelectric actuator of the present invention, the portions, ofthe piezoelectric layer and the vibration layer, which are opposed tothe through-hole, are deformed by changing the electric potential of theelectrodes. On the other hand, when the piezoelectric layer is heated toanneal, not only the piezoelectric layer but also the stacked basemember are heated simultaneously. For example, when the base member iscomposed of metal or silicon, the constitutive atoms thereof arediffused, for example, into the piezoelectric layer, when the basemember is heated at a high temperature. If the constitutive atoms of thebase member are diffused into the portion (driving portion, activeportion) of the piezoelectric layer facing the through-hole, then thepiezoelectric characteristic is deteriorated at the active portion ofthe piezoelectric layer, and the amounts of deformation of thepiezoelectric layer and the vibration layer, which are to be obtainedwhen the electric potential of the electrode is changed, areconsequently decreased.

However, in the present invention, the through-hole is formed for thebase member before performing the heating in order to anneal thepiezoelectric layer. Therefore, the constitutive atoms of the basemember are hardly diffused into the portion, of the piezoelectric layer,which faces the through-hole. Therefore, the piezoelectriccharacteristic of the active portion of the piezoelectric layer ishardly deteriorated. It is possible to suppress the decrease in theamounts of deformation of the piezoelectric layer and the vibrationlayer when the electric potential of the electrode is changed.

In order to sufficiently deform the vibration layer, it is necessarythat the length of the through-hole, which relates to the in-planedirection of the base member, should be increased for larger thicknessesof the vibration layer. However, when the vibration layer is formed asthe film on one surface of the base member, it is possible to thin thethickness of the vibration layer, for example, as compared with a casein which any sheet to serve as the vibration layer is joined to onesurface of the base member. Therefore, even when the length of thethrough-hole, which relates to the in-plane direction of the basemember, is small, the vibration layer is sufficiently deformed.Therefore, it is possible to decrease the length of the through-hole inrelation to the in-plane direction of the base member. It is possible tohighly integrate the active portions in the piezoelectric actuator.

In the method for producing the piezoelectric actuator of the presentinvention, the piezoelectric layer may be formed by an aerosoldeposition method.

When the piezoelectric layer is formed as the film by the aerosoldeposition method (AD method), it is necessary to perform the annealingin which the piezoelectric layer formed as the film is heated at a hightemperature in order to allow the piezoelectric layer to have thepiezoelectric characteristic. The constitutive atoms of the base memberare diffused by the heating. However, even in such a situation, thethrough-hole is formed through the base member before annealing thepiezoelectric layer. Therefore, the constitutive atoms of the basemember are hardly diffused into the portion, of the piezoelectric layer,which faces the through-hole. Therefore, the piezoelectriccharacteristic of the active portion of the piezoelectric layer ishardly deteriorated. It is possible to suppress the decrease in theamounts of deformation of the piezoelectric layer and the vibrationlayer when the electric potential of the electrode is changed.

In the method for producing the piezoelectric actuator of the presentinvention, the vibration layer may be formed by an aerosol depositionmethod.

When this procedure is adopted, the vibration layer, which has thedensified structure or arrangement, can be formed as the film at a highspeed by the AD method. When the vibration layer has the densifiedstructure, the diffused constitutive atoms of the base member arestopped at the vibration layer when the piezoelectric layer is heated inorder to perform the annealing. The constitutive atoms of the basemember are hardly diffused into the piezoelectric layer. Therefore, itis possible to effectively suppress the deterioration of thepiezoelectric characteristic of the piezoelectric layer.

Unlike the piezoelectric layer for which it is necessary to provide thepiezoelectric characteristic, it is unnecessary to perform the annealingfor the vibration layer formed by the AD method. The vibration layerformed by the AD method is solidified at the normal or ordinarytemperature. Therefore, it is unnecessary to heat the vibration layer ata high temperature when the vibration layer is formed as the film. Ifthe vibration layer is required to be heated at a high temperature(temperature higher than 600° C.) before the heating for annealing thepiezoelectric layer, it is assumed that the constitutive atoms of thebase member may be diffused into the portion of the vibration layeropposed to the through-hole. In this case, it is feared that theconstitutive atoms of the base member, which have been diffused to theportion of the vibration layer opposed to the through-hole, may befurther diffused into the piezoelectric layer during the heating to beperformed for annealing the piezoelectric layer thereafter. However,when the vibration layer is formed by the AD method, it is unnecessaryto heat to solidify the vibration layer. There is no fear of the furtherdiffusion of the constitutive atoms of the base member to thepiezoelectric layer as described above.

In the method for producing the piezoelectric actuator of the presentinvention, the through-hole may be formed by an etching. Accordingly,the through-hole can be easily formed for the base member composed ofmetal or silicon by means of the etching.

In the method for producing the piezoelectric actuator of the presentinvention, the forming of the electrode may include forming an exposedelectrode which is exposed on a side, of the piezoelectric layer, notfacing the vibration layer; and

the forming of the exposed electrode may be performed after the formingof the through-hole.

The exposed electrode is exposed on the side of the piezoelectric layeropposite to the vibration layer. Therefore, when the through-hole isformed by the etching, if the through-hole is formed after forming theexposed electrode, then it is feared that the exposed electrode may bedamaged by the etching solution. In order to avoid such aninconvenience, it is necessary to perform any extra step of, forexample, masking the exposed electrode before forming the through-holeby the etching. However, in the present invention, the exposed electrodeis formed after forming the through-hole. Therefore, the exposedelectrode is not damaged by the etching solution, which would beotherwise damaged as described above. It is unnecessary to perform, forexample, the masking treatment as described above. It is enough that theexposed electrode of the present invention is formed on the side of thepiezoelectric layer opposite to the vibration layer. In this context,the present invention also includes, for example, such an embodimentthat the exposed electrode is covered with, for example, any memberwhich is not the constitutive element of the present invention, and theexposed electrode is not exposed to the outside of the actuator.

In the method for producing the piezoelectric actuator of the presentinvention, the forming of the electrode may be performed before theannealing of the piezoelectric layer.

For example, when the electrode is formed by the screen printing, thesputtering method, or the like, it is necessary to perform the sinteringin order to fix or immobilize the formed electrode. In this procedure,when the electrode is formed before performing the heating in order toanneal the piezoelectric layer, the electrode can be simultaneouslysintered when the piezoelectric layer is annealed.

In the method for producing the piezoelectric actuator of the presentinvention, the forming of the electrode may include sintering theelectrode, and the sintering of the electrode may be performed beforethe forming of the through-hole and at a temperature lower than anannealing temperature to be adopted when the piezoelectric layer isannealed. Alternatively, the forming of the vibration layer may includesintering the vibration layer, and the sintering of the vibration layermay be performed before forming the through-hole and at a temperaturelower than an annealing temperature to be adopted when the piezoelectriclayer is annealed.

In any case, the sintering of the electrode or the vibration layer isperformed before forming the through-hole for the base member, but thesintering is performed at the temperature lower than the annealingtemperature for the piezoelectric layer. Therefore, the diffusion of theconstitutive atoms of the base member to the piezoelectric layer issuppressed during the sintering of the electrode or the vibration layer.In order to suppress the diffusion of the constitutive atoms of the basemember into the piezoelectric layer, the temperature of the sintering ofthe electrode or the vibration layer is preferably not more than 600° C.and more preferably not more than 500° C.

In the method for producing the piezoelectric actuator of the presentinvention, the electrode may be formed as a plurality of electrodesarranged on only one surface of the piezoelectric layer, and thepiezoelectric layer may be polarized in an in-plane direction of thepiezoelectric layer by using the plurality of electrodes. Further, theelectrode may be formed as a plurality of electrodes arranged on bothsurfaces of the piezoelectric layer to interpose the piezoelectric layertherebetween, and a portion of the piezoelectric layer, which isinterposed between the electrodes, may be polarized in a thicknessdirection of the piezoelectric layer. In any case, the constitutiveatoms of the base member are suppressed from the diffusion into thepiezoelectric layer. It is possible to enhance the piezoelectriccharacteristic of the piezoelectric layer.

According to a second aspect of the present invention, there is provideda method for producing a liquid transport apparatus, including:

providing a pressure chamber plate in which a pressure chamber is to beformed;

forming a vibration layer with a ceramics material on a surface of thepressure chamber plate;

forming a piezoelectric layer on a surface, of the vibration layer, notfacing the pressure chamber plate;

removing a part of the pressure chamber plate after forming thepiezoelectric layer to form the pressure chamber via which the vibrationlayer is exposed from a side, of the pressure chamber plate, not facingthe vibration layer;

forming an electrode at a portion, of the piezoelectric layer, whichfaces the pressure chamber; and

annealing the piezoelectric layer after forming the pressure chamber.The pressure chamber plate may be formed of metal or silicon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic arrangement of a printer according to anembodiment of the present invention.

FIG. 2 shows a plan view illustrating an ink-jet head shown in FIG. 1.

FIG. 3 shows a partial magnified view illustrating those shown in FIG.2.

FIG. 4 shows a sectional view taken along a IV-IV line shown in FIG. 3.

FIG. 5 shows a sectional view taken along a V-V line shown in FIG. 3.

FIG. 6 shows a flow chart illustrating the process for producing theink-jet head (piezoelectric actuator).

FIGS. 7A to 7E show states of the ink-jet head in respective steps ofthe production.

FIG. 8 shows a first modified embodiment as corresponding to FIG. 5.

FIGS. 9A to 9F show states of an ink-jet head in respective steps of theproduction of the ink-jet head in the first modified embodiment.

FIG. 10 shows a plan view illustrating the direction of the electricfield allowed to act on a piezoelectric layer and a part of an ink-jethead in a second modified embodiment.

FIG. 11 shows a plan view illustrating the direction of deformation ofthe piezoelectric layer and the part of the ink-jet head in the secondmodified embodiment.

FIG. 12 shows a sectional view taken along a XII-XII line shown in FIG.11.

FIG. 13 shows a sectional view taken along a XIII-XIII line shown inFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be explained below.

FIG. 1 shows a schematic arrangement of a printer according to theembodiment of the present invention. As shown in FIG. 1, the printer 1includes, for example, a carriage 2, an ink-jet head 3 (liquid transportapparatus), and a transport roller 4. The carriage 2 is reciprocativelymovable in the scanning direction (left-right direction as viewed inFIG. 1). The ink-jet head 3 is attached to the lower surface of thecarriage 2, and the ink-jet head 3 discharges the inks from a pluralityof nozzles 15 (see FIG. 2) formed on the lower surface thereof while theink-jet head 3 reciprocates in the scanning direction together with thecarriage 2. The transport roller 4 transports the recording paper P inthe paper feeding direction (direction directed toward the front of FIG.1). In the printer 1, the inks are discharged to the recording paper Pwhich is transported in the paper feeding direction by the transportroller 4, from the ink-jet head 3 which reciprocates in the scanningdirection together with the carriage 2, and thus the printing isperformed on the recording paper P.

Next, the ink-jet head 3 will be explained. FIG. 2 shows a plan viewillustrating the ink-jet head 3 shown in FIG. 1. FIG. 3 shows a partialmagnified view illustrating those shown in FIG. 2. FIG. 4 shows asectional view taken along a IV-IV line shown in FIG. 3. FIG. 5 shows asectional view taken along a V-V line shown in FIG. 3. As shown in FIGS.2 to 5, the ink-jet head 3 includes a channel unit (flow passage unit)31 which is formed with ink channels (flow passages) including pressurechambers 10, and a piezoelectric actuator 32 which is provided in orderto apply the pressure to the ink contained in the pressure chamber 10.

The channel unit 31 is constructed by mutually stacking four plates of acavity plate 21 (pressure chamber plate, base member), a base plate 22,a manifold plate 23, and a nozzle plate 24. The plates 21 to 24, exceptthe nozzle plate 24, are composed of a metal material such as stainlesssteel. The nozzle plate 24 is composed of a synthetic resin such aspolyimide. Alternatively, the nozzle plate 24 may be also composed of ametal material in the same manner as the other three plates 21 to 23.

The cavity plate 21 is formed with the plurality of pressure chambers10. The plurality of pressure chambers 10 have substantially ellipticshapes in which the scanning direction (left-right direction as viewedin FIG. 2) is the longitudinal direction as viewed in a plan view (asviewed in the thickness direction perpendicular to the in-planedirection of the cavity plate 21). The plurality of pressure chambers 10are formed as through-holes which penetrate through the cavity plate 21in the thickness direction. The plurality of pressure chambers 10 formtwo arrays of the pressure chambers which extend in the paper feedingdirection (upward-downward direction as viewed in FIG. 2) respectively.Substantially circular through-holes 12, 13 are formed respectively atpositions of the base plate 22 overlapped with both ends of the pressurechambers 10 in relation to the longitudinal direction as viewed in aplan view.

The manifold plate 23 is formed with a manifold channel (manifold) 11. Apart of the manifold channel (extending portions of the manifoldchannel) extends in two arrays in the paper feeding direction along thearrays of the pressure chambers 10 and a part of the manifold channel (aconnecting portion of the manifold channel) extends in the scanningdirection at the lower end as shown in FIG. 2 so that the extendingportions, which extend in the paper feeding direction, are connected toone another. The extending portions of the manifold channel 11, whichextend in the two arrays in the paper feeding direction as describedabove, are arranged to be overlapped with substantially right halves ofthe plurality of pressure chambers 10 arranged on the right side asshown in FIG. 2 as viewed in a plan view and substantially left halvesof the plurality of pressure chambers 10 arranged on the left side asshown in FIG. 2 respectively. The ink is supplied to the manifoldchannel 11 from an ink supply port 9 which is formed at the lower end(at the connecting portion) as shown in FIG. 2. Substantially circularthrough-holes 14 are formed at portions of the manifold plate 23overlapped with the through-holes 13 as viewed in a plan view. Nozzles15 are formed at portions of the nozzle plate 24 overlapped with thethrough-holes 14 as viewed in a plan view.

The manifold channel 11 is communicated with the pressure chambers 10via the through-holes 12. Each of the pressure chambers 10 iscommunicated with one of the nozzles 15 via one of the through-holes 13,14. In this way, a plurality of individual ink channels are formed fromthe outlets of the manifold channel 11 via the pressure chambers 10 toarrive at the nozzles 15.

The piezoelectric actuator 32 includes a vibration layer 41, apiezoelectric layer (layer including a piezoelectric material) 42, acommon electrode 43, and a plurality of individual electrodes 44. Thevibration layer 41 is formed of a ceramics material such as alumina orzirconia. The vibration layer 41 is arranged on the upper surface of thecavity plate 21 so that the plurality of pressure chambers 10 arecovered therewith.

The piezoelectric layer 42 is a layer which includes the piezoelectricmaterial containing a major component of lead titanate zirconate as amixed crystal of lead titanate and lead zirconate. The piezoelectriclayer 42 is arranged continuously to range over (to cover) the pluralityof pressure chambers 10 on the upper surface of the vibration layer 41(on the side opposite to the cavity plate 21). The piezoelectric layer42 is previously polarized in the thickness direction thereof.

The common electrode 43 is formed of, for example, platinum, palladium,gold, or silver. The common electrode 43 is arranged to range over thesubstantially entire region between the vibration layer 41 and thepiezoelectric layer 42. The common electrode 43 is connected to anunillustrated driver IC via an unillustrated flexible printed circuit(FPC). The common electrode 43 is always retained at the ground electricpotential by the driver IC.

The plurality of individual electrodes 44 (exposed electrodes) areformed of a material which is the same as or equivalent to that of thecommon electrode 43. The plurality of individual electrodes 44 (exposedelectrodes) are arranged on the upper surface of the piezoelectric layer42 (on the side opposite to the vibration layer 41) corresponding to theplurality of pressure chambers 10. The plurality of individualelectrodes 44 (exposed electrodes) are exposed on the upper surface ofthe piezoelectric layer 42. The individual electrodes 44 havesubstantially elliptic shapes, as viewed in a plan view, which are onesize smaller than the pressure chambers 10. The individual electrodes 44are arranged at portions of the upper surface of the piezoelectric layer42 overlapped with substantially central portions of the pressurechambers 10 as viewed in a plan view. An end of the individual electrode44, which is disposed on the side opposite to the nozzle 15 in thelongitudinal direction, is extracted in the scanning direction to extendto a portion of the upper surface of the piezoelectric layer 42 notopposed to the pressure chamber 10. The forward end thereof is aconnecting terminal 44 a to be connected to unillustrated FPC. Thedriving electric potential is selectively applied to the plurality ofindividual electrodes 44 by the unillustrated driver IC through the FPC.

A method for driving the piezoelectric actuator 32 will now beexplained. The plurality of individual electrodes-32 are previouslyretained at the ground electric potential in the piezoelectric actuator32. When the piezoelectric actuator 32 is driven, the driving electricpotential is selectively applied to any one of the plurality ofindividual electrodes 44. Accordingly, the electric potential differenceis generated between the individual electrode 44 of the piezoelectriclayer 42 to which the driving electric potential is applied and thecommon electrode 43 which is retained at the ground electric potential.The electric field in the thickness direction is generated at the activeportions of the piezoelectric layer 42 interposed between theseelectrodes.

The direction of the electric field is coincident with the direction ofpolarization of the piezoelectric layer 42. Therefore, the portion(active portion) of the piezoelectric layer 42, which is opposed to thepressure chamber 10, is shrunk in the horizontal direction perpendicularto the direction of the electric field. In accordance therewith, theportions of the piezoelectric layer 42 and the vibration layer 41, whichare opposed to the pressure chamber 10, are deformed so that theyprotrude toward the pressure chamber 10 as a whole. Accordingly, thevolume of the pressure chamber 10 is lowered (decreased), and thepressure of the ink contained in the pressure chamber 10 is raised(pressure is applied to the ink contained in the pressure chamber 10).The ink is discharged from the nozzle 15 communicated with the pressurechamber 10.

Next, a method for producing the ink-jet head 3 (piezoelectric actuator32) will be explained. FIG. 6 shows a flow chart illustrating the stepsof producing the ink-jet head 3. FIG. 7 shows the steps to illustratestates of the ink-jet head 3 in the respective steps of the production.

When the ink-jet head 3 (piezoelectric actuator 32) is produced, atfirst, as shown in FIGS. 6 and 7A, the vibration layer 41 is formed asthe film by means of the aerosol deposition method (AD method) in whichthe aerosol containing fine particles of the ceramics material isallowed to blow against the upper surface (one surface) of the cavityplate 21 (base member) before forming the pressure chambers 10 (StepS101, hereinafter simply referred to, for example, as “S101”: vibrationlayer-forming step). When the vibration layer 41 is formed by the ADmethod as described above, then the vibration layer 41 has the densifiedstructure, and it is possible to thin the thickness thereof.

In this arrangement, in order to sufficiently deform the vibration layer41 when the piezoelectric actuator 32 is driven as described above, itis necessary that the lengths of the pressure chamber 10, which relateto the scanning direction and the paper feeding direction (in-planedirection of the cavity plate 21), should be increased for largerthicknesses of the vibration layer 41.

The thin vibration layer 41 is formed as the film by means of the ADmethod as in this embodiment. Therefore, the vibration layer 41 issufficiently deformed when the piezoelectric actuator 32 is driven, evenwhen the lengths of the pressure chamber 10, which relate to thescanning direction and the paper feeding direction, are small.Therefore, it is possible to highly integrate the pressure chambers 10and the driving portions of the piezoelectric actuator 32 (portionsopposed to the pressure chambers 10).

Subsequently, as shown in FIGS. 6 and 7B, the common electrode 43 isformed on the upper surface of the vibration layer 41, for example, bymeans of the screen printing or the sputtering method (S102).Subsequently, as shown in FIGS. 6 and 7C, the piezoelectric layer 42 isformed as the film on the upper surface of the vibration layer 41 onwhich the common electrode 43 has been formed (on the side opposite tothe cavity plate 21) by means of the AD method in which the film isformed such that the aerosol containing the fine particles of thepiezoelectric material is allowed to blow (S103: piezoelectriclayer-forming step).

Subsequently, as shown in FIGS. 6 and 7D, parts of the cavity plate 21are removed, and thus the pressure chambers 10 (through-holes), whichpenetrate through the cavity plate 21 in the thickness direction thereofand which are capable of facing the vibration layer 41 from the lowerpositions (from the side of the cavity plate 21 opposite to thevibration layer 41), are formed for the cavity plate 21 (S104:through-hole-forming step, pressure chamber-forming step). In thisarrangement, the cavity plate 21 is formed of the metal material such asstainless steel. Therefore, the pressure chambers 10 can be formed withease by means of the etching.

Subsequently, as shown in FIGS. 6 and 7E, the plurality of individualelectrodes 44 are formed on the upper surface of the piezoelectric layer42, for example, by means of the screen printing or the sputteringmethod (S105: exposed electrode-forming step).

Contrary to the embodiment of the present invention, it is also possibleto form the pressure chambers 10 for the cavity plate 21 by means of theetching after forming the plurality of individual electrodes 44 on theupper surface of the piezoelectric layer 42. However, in this procedure,the individual electrodes 44 are exposed on the upper surface of thevibration layer 42. Therefore, the etching solution is stuck to theindividual electrodes 44 when the pressure chambers 10 are formed forthe cavity plate 21 by means of the etching. It is feared that theindividual electrodes 44 may be damaged. Further, in order to avoid thisinconvenience, it is necessary to perform any extra step, for example,such that the individual electrodes 44 are masked before forming thepressure chambers 10 by means of the etching.

On the contrary, in the embodiment of the present invention, theindividual electrodes 44 are formed after forming the pressure chambers10. In other words, the exposed electrode-forming step is performedafter the through-hole-forming step. Therefore, the individualelectrodes 44 are not damaged by the etching solution, and it is alsounnecessary, for example, to mask the individual electrodes 44.Therefore, the production steps are simplified corresponding thereto.The combination of the step of forming the common electrode describedabove and the step of forming the individual electrodes 44 correspondsto the electrode-forming step of forming the electrodes at the portionsof the piezoelectric layer 42 opposed to at least the pressure chambers10.

Subsequently, the stack of the cavity plate 21, the vibration layer 41,the common electrode 43, the piezoelectric layer 42, and the pluralityof individual electrodes 44 is heated at a predetermined annealingtemperature (for example, about 850° C.) (S106: heating step).Accordingly, the annealing is performed, in which the heating iseffected at the high temperature in order to provide the piezoelectriccharacteristic for the piezoelectric layer 42 formed by the AD method.Further, the common electrode 43 and the individual electrodes 44 aresintered. The annealing of the piezoelectric layer is performed in orderthat the crystal grain size of the piezoelectric material is increasedto increase the piezoelectric constant. The sintering of the electrodeis performed in order that the surfaces of the metal particles to serveas the material for the electrode are fixed or immobilized to thesurface of the substrate (for example, the piezoelectric layer and thevibration layer) while bonding the surfaces of the metal particles toone another. The “annealing” and the “sintering” are distinctlydistinguished from each other.

In this situation, the constitutive atoms of the cavity plate 21 (forexample, Cr atoms when the cavity plate 21 is composed of stainlesssteel) are diffused toward the vibration layer 41 and the piezoelectriclayer 42 in accordance with the heating described above. When theconstitutive atoms of the cavity plate 21 are diffused into the portionsof the piezoelectric layer 42 opposed to the pressure chambers 10, thepiezoelectric characteristic is deteriorated at the concerning portionsof the piezoelectric layer 42. As a result, the amounts of deformation,of the piezoelectric layer 42 and the vibration layer 41, which areobtained when the piezoelectric actuator 32 is driven, are decreased.The discharge characteristic of the ink discharged from the nozzles 15is deteriorated.

However, in the embodiment of the present invention, the pressurechambers 10 are formed through the cavity plate 21 by means of theetching before performing the heating. As described above, the pressurechambers 10 are formed as the through-holes in the cavity plate 21.Therefore, the area of the piezoelectric layer 42, which is overlappedwith the pressure chambers 10, is not overlapped with the metal platewhich constitutes the cavity plate 21. Therefore, even if theconstitutive atoms of the cavity plate 21 are diffused toward thevibration layer 41 and the piezoelectric layer 42, the constitutiveatoms are hardly diffused into the portions of the piezoelectric layer42 opposed to the pressure chambers 10. Therefore, it is possible tosuppress the deterioration of the piezoelectric characteristic of theportions of the piezoelectric layer 42 opposed to the pressure chambers10, and it is possible to suppress the decrease in the amounts ofdeformation of the piezoelectric layer 42 and the vibration layer 41when the piezoelectric actuator 32 is driven.

The vibration layer 41 of the ceramics material is formed by the ADmethod between the upper surface of the cavity plate 21 and thepiezoelectric layer 42 as described above. In this way, the vibrationlayer 41 is formed by the AD method, and hence the vibration layer 41has the densified structure. The constitutive atoms, which are diffusedfrom the cavity plate 21, are stopped by the vibration layer 41, and theconstitutive atoms are hardly diffused to the piezoelectric layer 42.Accordingly, the decrease in the piezoelectric characteristic is furthersuppressed at the portions of the piezoelectric layer 42 overlapped withthe pressure chambers.

In the embodiment of the present invention, the heating step describedabove is performed after forming the common electrode 43 and theplurality of individual electrodes 44. In this way, theelectrode-forming step is performed before the heating step. Therefore,it is possible to simultaneously perform the annealing of thepiezoelectric layer 42 and the sintering of the common electrode 43 andthe individual electrodes 44.

After that, the cavity plate 21 is mutually joined to the base plate 22,the manifold plate 23, and the nozzle plate 24 which are previouslymanufactured (S107). Accordingly, the ink-jet head 3 is completed. It isnecessary to perform the polarizing step in order to polarize thepiezoelectric layer after the heating step (S106). The portion (activeportion) of the piezoelectric layer, which is interposed between thecommon electrode 43 and the individual electrodes 44, is polarized inthe thickness direction, for example, by retaining the common electrode43 at the ground electric potential and allowing the individualelectrode 44 to have an electric potential higher than the drivingelectric potential.

In relation to the embodiment explained above, when the piezoelectriclayer 42 is formed by the AD method, it is necessary to perform theannealing in which the piezoelectric layer 42 is heated at the hightemperature in order to allow the piezoelectric layer 42 to have thepiezoelectric characteristic. In this situation, the constitutive atomsof the cavity plate 21 to be heated together with the piezoelectriclayer 42 are diffused toward the vibration layer 41 and thepiezoelectric layer 42.

However, in the embodiment of the present invention, the parts of thecavity plate 21 are removed to form the pressure chambers 10 beforeheating the stack of the cavity plate 21, the vibration layer 41, thecommon electrode 43, the piezoelectric layer 42, and the individualelectrodes 44. In other words, the area of the piezoelectric layer,which serves as the active portion, is not overlapped with the metalportion of the cavity plate 21. Therefore, even when the constitutiveatoms of the cavity plate 21 are diffused by the heating to be performedthereafter, the constitutive atoms of the cavity plate 21 are hardlydiffused to the portions of the piezoelectric layer 42 opposed to thepressure chambers 10. Accordingly, it is possible to suppress thedeterioration of the piezoelectric characteristic of the area of thepiezoelectric layer 42 to serve as the active portion.

In the embodiment of the present invention, the vibration layer 41 isformed as the film by the AD method. Therefore, the vibration layer 41,which has the densified structure, can be formed as the film at a highspeed. Owing to the fact that the vibration layer 41, which is arrangedbetween the cavity plate 21 and the piezoelectric layer 42, has thedensified structure, the constitutive atoms of the cavity plate 21,which are diffused during the heating (annealing of the piezoelectriclayer), are stopped at the vibration layer 41, and the constitutiveatoms of the cavity plate 21 are hardly diffused to the piezoelectriclayer 42. Therefore, it is possible to effectively suppress thedeterioration of the piezoelectric characteristic of the portions of thepiezoelectric layer 42 opposed to the pressure chambers 10.

In order to sufficiently deform the vibration layer 41 when thepiezoelectric actuator 32 is driven, it is necessary to increase thelengths of the pressure chambers 10 in the scanning direction and/or thepaper feeding direction for larger thicknesses of the vibration layer41. In the embodiment of the present invention, the vibration layer 41is formed as the film by the AD method, and hence the vibration layer 41can be thinned. Therefore, even when the lengths of the pressurechambers 10 in the scanning direction and/or the paper feeding directionare small, it is possible to sufficiently deform the vibration layer 41.Therefore, it is possible to highly integrate the pressure chambers 10and driving portions of the piezoelectric actuator 32 opposed to thepressure chambers 10. Here, the driving portions of the piezoelectricactuator 32 includes one of the individual electrodes 44, the commonelectrode 43, and one of the active portions of the piezoelectric layerwhich is located between the electrodes 43, 44.

The cavity plate 21 is formed of the metal material such as stainlesssteel. Therefore, the pressure chambers 10 can be easily formed for thecavity plate 21 by the etching.

The individual electrodes 44 are formed on the upper surface of thepiezoelectric layer 42 after forming the pressure chambers 10 for thecavity plate 21 by the etching. Therefore, the individual electrodes 44are not damaged, which would be otherwise damaged such that the etchingsolution is stuck to the individual electrodes 44 when the pressurechambers 10 are formed. Accordingly, it is unnecessary to perform anyextra step of masking the individual electrodes 44 before performing theetching.

In the embodiment of the present invention, the stack of the cavityplate 21, the vibration layer 41, the common electrode 43, thepiezoelectric layer 42, and the individual electrodes 44 is heated afterforming the individual electrodes 44. Therefore, the annealing of thepiezoelectric layer 42 and the sintering of the individual electrodes 44and the common electrode 43 can be simultaneously performed.

Next, modified embodiments, in which various modifications are appliedto the embodiment of the present invention, will be explained. However,those constructed in the same manner as those of the embodiment of thepresent invention are designated by the same reference numerals, anyexplanation of which will be appropriately omitted.

In the embodiment of the present invention, the piezoelectric layer 42is formed as the film by the AD method. However, the piezoelectric layer42 can be also formed by any other method. Specifically, for example,the piezoelectric layer 42 may be formed as a film such that a slurry ina form of liquid, which is prepared by mixing a solvent with a rawmaterial powder composed of a piezoelectric material and asintering-auxiliary (a sintering aid) such as glass, an organic binder,and a plasticizer, is applied to the upper surface of the vibrationlayer 41 formed with the common electrode 43. In this procedure, it isnecessary to sinter (solidify) the piezoelectric layer 42 after applyingthe slurry.

In the embodiment described above, the piezoelectric layer 42 is formedby the AD method. The vibration layer 41 and the piezoelectric layer 42,which are formed as the films by the AD method, are solidified at thenormal or ordinary temperature. Therefore, it is unnecessary to performthe sintering of the piezoelectric layer. In the embodiment describedabove, the annealing treatment is performed, in which the piezoelectriclayer 42 is heated at the high temperature. However, as described above,the annealing of the piezoelectric layer is the treatment to allow thepiezoelectric layer to have the piezoelectric characteristic, which isnot the treatment to solidify the piezoelectric layer.

When the piezoelectric layer is formed as the film by applying theslurry, the stack of the cavity plate 21, the vibration layer 41, thecommon electrode 43, the piezoelectric layer 42, and the individualelectrodes 44 is heated at a high temperature (for example, not lessthan 850° C.) in order to sinter (solidify) the piezoelectric layer 42and anneal the piezoelectric layer 42 after applying the slurry. In thisprocedure, the piezoelectric layer is simultaneously sintered as well byannealing the piezoelectric layer without distinctly perform thesintering of the piezoelectric layer. Also in this case, theconstitutive atoms of the cavity plate 21 are diffused when thepiezoelectric layer 42 is heated. However, the piezoelectric layer 42 isheated after forming the pressure chambers 10 for the cavity plate 21 inthe same manner as in the embodiment. Therefore, the constitutive atomsof the cavity plate 21 are hardly diffused into the portions of thepiezoelectric layer 42 opposed to the pressure chambers 10.

In the embodiment of the present invention, the vibration layer 41 isalso formed as the film by the AD method. However, the vibration layer41 can be formed as the film by any other method. When the vibrationlayer 41 is formed by the AD method as in the embodiment describedabove, the vibration layer 41, which has been formed as the film, can besolidified at the normal temperature. Therefore, there is no fear of thediffusion of the constitutive atoms from the base member 21 when thevibration layer 41 is solidified. However, the vibration layer 41 can bealso formed as a film by any method including, for example, the sol-gelmethod, the sputtering method, the CVD method (chemical vapor depositionmethod), and the hydrothermal method without being limited to the ADmethod, provided that the vibration layer 41 can be solidified at a lowtemperature of such an extent that the constitutive atoms are notdiffused from the cavity plate 21.

In this procedure, it is necessary to solidify the vibration layer 41 inorder to form, for example, the common electrode 43 on the upper surfaceafter forming the vibration layer 41. Further, the pressure chambers(through-holes) 10 cannot be formed for the cavity plate 21 beforesolidifying the vibration layer 41. If the stack of the cavity plate 21and the vibration layer 41 is heated at a high temperature to such anextent that the constitutive atoms of the cavity plate 21 are diffused,in order to solidify the vibration layer 41, the constitutive atoms ofthe cavity plate 21 are diffused into the entire region of the vibrationlayer 41 during the heating. In other words, the constitutive atoms ofthe cavity plate 21 are also diffused into the portions of the vibrationlayer 41 to be overlapped with the pressure chambers 10. Therefore, whenthe pressure chambers 10 are formed for the cavity plate 21 thereafter,and the heating is performed in order to perform the annealing for thepiezoelectric layer 42, then it is feared that the constitutive atoms ofthe cavity plate 21, which have been diffused into the portions of thevibration layer 41 overlapped with the pressure chambers 10, may befurther diffused from the vibration layer 41 to the portions of thepiezoelectric layer 42 overlapped with the pressure chambers 10, and thepiezoelectric characteristic may be deteriorated at the portions of thepiezoelectric layer 42 overlapped with the pressure chambers 10.

Therefore, it is preferable that the vibration layer 41 is formed as thefilm by using any method which makes it possible to effect thesolidification at a low temperature to such an extent that theconstitutive atoms of the cavity plate 21 are not diffused.

In the embodiment of the present invention, the pressure chambers 10 areformed for the cavity plate 21, and then the individual electrodes 44are formed on the upper surface of the piezoelectric layer 42. However,the individual electrodes 44 may be formed on the upper surface of thepiezoelectric layer 42, and then the pressure chambers 10 may be formedfor the cavity plate 21. In this procedure, in order to avoid any damageof the individual electrodes 44 caused by the etching solution, theindividual electrodes 44 may be masked before forming the pressurechambers 10 for the cavity plate 21 by the etching.

In the embodiment of the present invention, the individual electrodes 44are formed, and then the stack of the cavity plate 21, the vibrationlayer 41, the common electrode 43, the piezoelectric layer 42, and theindividual electrodes 44 is heated to simultaneously perform theannealing of the piezoelectric layer 42 and the sintering of theelectrodes (individual electrodes 44 and common electrode 43). However,the present invention is not limited thereto. For example, the stack ofthe cavity plate 21, the vibration layer 41, the common electrode 43,and the piezoelectric layer 42 may be heated to anneal the piezoelectriclayer 42 and sinter the common electrode 43 before forming theindividual electrodes 44 after forming the pressure chambers 10 for thecavity plate 21, and then the individual electrodes 44 may be formed onthe upper surface of the piezoelectric layer 42. The stack stacked withthe individual electrodes 44 may be heated distinctly from the above inorder to sinter the formed individual electrodes 44.

If the sintering of the electrode (for example, the individual electrodeand/or the common electrode) or the sintering of the vibration layer isperformed distinctly from the annealing of the piezoelectric layer, thesintering step can be also performed before the through-holes, whichserve as the pressure chambers, are formed for the cavity plate.However, in order to avoid the diffusion of the metal atoms or the likefrom the cavity plate into the piezoelectric layer and the deteriorationof the piezoelectric characteristic of the piezoelectric layer, it isnecessary to perform the sintering at a temperature which is lower thanat least the annealing temperature. Specifically, it is preferable tosinter, for example, the electrodes and the vibration layer at atemperature of not more than 600° C., for the following reason. That is,according to the knowledge of the present inventors, if the heating iseffected to a high temperature exceeding 600° C., then the diffusion ofthe metal atoms or the like is conspicuous, and it is seriously fearedthat the piezoelectric characteristic of the piezoelectric layer may bedeteriorated. It is more preferable to sinter, for example, theelectrodes and the vibration layer at a temperature of not more than500° C., for the following reason. That is, according to the knowledgeof the present inventors, even if the heating is effected to a lowtemperature of not more than 500° C., then the influence of thediffusion of the metal atoms or the like is small, and it is scarcelyfeared that the piezoelectric characteristic of the piezoelectric layermay be deteriorated.

The present invention is not limited to the arrangement in which thecavity plate is formed of the metal material such as stainless steel.The cavity plate may be formed of silicon. When the atoms of silicon arediffused into the piezoelectric layer 42, the piezoelectriccharacteristic of the piezoelectric layer 42 is also deteriorated.However, even when the cavity plate 21 is formed of silicon, parts ofthe cavity plate 21 are removed to form the pressure chambers 10 beforeperforming the heating. Therefore, the atoms of silicon are hardlydiffused into the portions of the piezoelectric layer 42 opposed to thepressure chamber 10 in the same manner as in the embodiment. Further,when the base member, which is to serve as the cavity plate, is composedof silicon, the pressure chambers can be also formed for the base memberby means of the etching with ease.

In the embodiment of the present invention, only one layer of thepiezoelectric layer 42 is formed on the upper surface of the vibrationlayer 41. However, the present invention is not limited thereto. In afirst modified embodiment, as shown in FIG. 8, piezoelectric layers 71,72 are further arranged on the upper surface of the piezoelectric layer42. A common electrode 73, which covers the substantially entire regionsof the piezoelectric layers 71, 72 (which covers all of the pressurechambers), is arranged between the piezoelectric layer 71 and thepiezoelectric layer 72, and individual electrodes 74 (exposedelectrodes), which have the same or equivalent shapes as the shapes ofthe individual electrodes 44, are arranged at portions of the uppersurface of the piezoelectric layer 72 (on the side opposite to thevibration layer 41) overlapped with the pressure chambers 10. In thisarrangement, the combination of the piezoelectric layers 42, 71, 72corresponds to the piezoelectric layer according to the presentinvention. In this embodiment, unlike the embodiment described above,the individual electrodes 44 do not correspond to the exposed electrodesaccording to the present invention.

When such an ink-jet head is produced, the following procedure isadopted in the same manner as in the embodiment of the presentinvention. That is, the vibration layer 41, the common electrode 43, andthe piezoelectric layer 42 are formed on the upper surface of the cavityplate 21 before forming the pressure chambers 10 as shown in FIGS. 7A to7C, and then the individual electrodes 44 are formed on the uppersurface of the piezoelectric layer 42 as shown in FIG. 9A. Subsequently,the piezoelectric layer 71 is formed as the film on the upper surface ofthe piezoelectric layer 42 as shown in FIG. 9B. Subsequently, the commonelectrode 73 is formed on the upper surface of the piezoelectric layer71 as shown in FIG. 9C, and then the piezoelectric layer 72 is formed onthe upper surface of the piezoelectric layer 71 as shown in FIG. 9D. Thepiezoelectric layers 71, 72 are formed as the films by the AD method inthe same manner as the piezoelectric layer 42. The common electrode 73is formed, for example, by the screen printing or the sputtering methodin the same manner as the common electrode 43.

Subsequently, the pressure chambers 10 are formed for the cavity plate21 by the etching (through-hole-forming step, pressure chamber-formingstep) as shown in FIG. 9E in the same manner as in the embodiment of thepresent invention, and then the individual electrodes 74 are formed, forexample, by the screen printing or the sputtering method on the uppersurface of the piezoelectric layer 72 (exposed electrode-forming step)as shown in FIG. 9F. After that, the stack of the cavity plate 21, thevibration layer 41, the piezoelectric layers 42, 71, 72, the commonelectrodes 43, 73, and the individual electrodes 44, 74 is heated toanneal the piezoelectric layers 42, 71, 72 and sinter the commonelectrodes 43, 73 and the individual electrodes 44, 74 (heating step).

In this case, the combination of the steps of forming the films of thepiezoelectric layers 42, 71, 72 corresponds to the piezoelectriclayer-forming step according to the present invention, and thecombination of the steps of forming the common electrodes 43, 73 and theindividual electrodes 44, 74 corresponds to the electrode-forming stepaccording to the present invention.

Even in this case, the individual electrodes 74 are formed after formingthe pressure chambers 10 for the cavity plate 21 by the etching.Therefore, the individual electrodes 74 are not damaged by the etchingsolution. Further, the heating step is performed after forming theindividual electrodes 74. Therefore, the individual electrodes 74 can besintered simultaneously with the annealing of the piezoelectric layers42, 71, 72 and the sintering of the common electrodes 43, 73 and theindividual electrodes 44.

In the embodiment of the present invention, the common electrode 43 isarranged on the lower surface of the piezoelectric layer 42 in thepiezoelectric actuator 32, and the plurality of individual electrodes 44are arranged on the upper surface of the piezoelectric layer 42.However, the electrodes may be arranged on only the upper surface of thepiezoelectric layer 42 in the piezoelectric actuator or may be arrangedonly on the lower surface of the piezoelectric layer 42 in thepiezoelectric actuator.

For example, in a second modified embodiment, as shown in FIGS. 10 to13, any electrode is not formed on the lower surface of thepiezoelectric layer 42, and individual electrodes 132 and a commonelectrode 134 are formed on the upper surface of the piezoelectric layer42.

The plurality of individual electrodes 132 are formed on upper surfacesof a plurality of inner areas 140 of the piezoelectric layer 42overlapped with the plurality of pressure chambers 10 respectively. Thearea of the piezoelectric layer 42, which is not overlapped with theplurality of pressure chambers 10, is referred to as “outer area 141”.Each of the substantially elliptic inner areas includes a first zone 142which includes the center of the inner area 140 and which is slender inthe longitudinal direction (left-right direction as viewed in FIG. 10),and second zones 143 which are positioned between the outer edges of thefirst zone 142 and the boundary between the inner area 140 and the outerarea 141 and which are overlapped with the vicinity portions of the edgeof the pressure chamber 10. The pattern of each of the individualelectrodes 132 includes three longitudinal-projections 145 which extendin the longitudinal direction of the pressure chamber 10 (inner area140), and a plurality of widthwise-projections 146 which extendoutwardly in the widthwise direction respectively from the twolongitudinal-projections 145 positioned on the outer side in thewidthwise direction of the pressure chamber 10. The threelongitudinal-projections 145 are arranged while being separated fromeach other by equal spacing distances in the widthwise direction on anupper surface of the first zone 142. On the other hand, the plurality ofwidthwise-projections 146 are arranged while being separated from eachother by equal spacing distances in the longitudinal direction on uppersurfaces of the second zones 143.

The three longitudinal-projections 145 mutually make conduction at theirfirst ends (right ends as viewed in FIG. 10). A contact section 135 isled from the conduction portion to the outer area 141. The plurality ofcontact sections 135, which correspond to the plurality of individualelectrodes 132 respectively, are arranged in the paper feeding directionrespectively at the both ends in the scanning direction. Further, anunillustrated wiring member such as FPC is joined to the plurality ofcontact sections 135. The contact sections 135 are electricallyconnected to an unillustrated driver IC via the wiring member. The threelongitudinal-projections 145 in the first zone 142, the plurality ofwidthwise-projections 146 in the second zones 143, and the contactsection 135 mutually make the conduction, and hence the driving voltageis simultaneously applied from the driver IC via FPC and the contactsection 135 to the three longitudinal-projections 145 and the pluralityof widthwise-projections 146.

The pattern of the common electrode 134 includes twolongitudinal-projections 147 which extend in the longitudinal directionof the pressure chamber 10 respectively between the threelongitudinal-projections 145 of the individual electrode 132 of each ofthe first zones 142, and a plurality of widthwise-projections 148 whichextend in the widthwise direction (transverse direction) of the pressurechamber 10 respectively between the plurality of widthwise-projections146 of the individual electrode 132 of each of the second zones 143. Asshown in FIG. 10, the three longitudinal-projections 145 of theindividual electrode 132 and the two longitudinal-projections 147 of thecommon electrode 134 are arranged alternately while being separated fromeach other by equal spacing distances in the first zone 142. Theplurality of widthwise-projections 146 of the individual electrode 132and the plurality of widthwise-projections 148 of the common electrode134 are arranged alternately while being separated from each other byequal spacing distances in the second zone 143.

As shown in FIG. 10, all of the longitudinal-projections 147 of thefirst zones 142, which correspond to the two arrays of the pressurechambers 10 of the left and right arrays respectively, make conductionby a conducting section 149 which extends in the direction ofarrangement of the pressure chambers 10 (upward-downward direction asviewed in FIG. 10) at the ends (lefts ends as shown in FIG. 10) disposedon the side opposite to the contact sections 135. Thewidthwise-projections 148 of the second zones 143 are connected byconducting sections 150 which extend in the longitudinal direction(left-right direction as viewed in FIG. 10) between the two adjoiningpressure chambers 10. The conducting sections 150 are connected to theconducting section 149. In other words, the longitudinal-projections 147and the widthwise-projections 148 of the common electrode 134 mutuallymake conduction by the aid of the conducting sections 149, 150. Thewidthwise-projections 148 include first widthwise-projections 148 awhich extend toward one side (upper side as viewed in FIG. 10) in thewidthwise direction of the pressure chamber 10 from the conductingsection 150, and second widthwise-projections 148 b which extend towardthe other side (lower side as viewed in FIG. 10) in the widthwisedirection. Both of the first widthwise-projections 148 a and the secondwidthwise-projections 148 b function as the common electrode 134 fordriving the two adjoining pressure chambers 10. In other words, thefirst widthwise-projections 148 a and the second widthwise-projections148 b, which contribute to the driving of the different pressurechambers 10 respectively, are branched from one conducting section 150in this structure. The common electrode 134 is efficiently arranged inthe limited space. Although not shown in the drawings, two contactsections are led for the two left and right conducting sections 149respectively to arrive at the both ends in the scanning direction(disposed at the same positions as those of the contact sections 135 ofthe individual electrodes 132 in relation to the scanning direction).FPC is joined to the two contact sections in the same manner as thecontact sections 135 of the individual electrodes 132. All of thelongitudinal-projections 147 and the widthwise-projections 148 of thecommon electrode 134 are always retained at the ground electricpotential by the aid of the contact sections and the wiring member suchas FPC as described above.

In this way, both of the pattern of the individual electrodes 132 andthe pattern of the common electrode 134 are formed on the upper surfaceof the piezoelectric layer 42. Therefore, when the driving voltage isapplied to a certain individual electrode 132, the electric field, whichis directed in the direction (in-plane direction) parallel to thesurface, is generated in the piezoelectric layer 42 (especially in theupper surface portion) of the inner area 140. As shown in FIG. 10, thefirst electric field E1, which is composed of the in-plane componentdirected in the widthwise direction of the pressure chamber 10, isgenerated as indicated by arrows between the longitudinal directionprojections 145 of the individual electrode 132 and the longitudinaldirection projections 147 of the common electrode 134 in the first zone142. On the other hand, the second electric field E2, which is composedof the in-plane component directed in the longitudinal direction of thepressure chamber 10 perpendicular to the first electric field E1, isgenerated as indicated by arrows between the widthwise directionprojections 146 of the individual electrode 132 and the widthwisedirection projections 148 of the common electrode 134 in the second zone143.

The inner area 140 of the piezoelectric layer 42 is subjected to thepolarizing treatment in the direction parallel to the surface bypreviously allowing the high electric field to act by applying thepolarizing voltage higher than the driving voltage described above tothe individual electrode 132. The polarization is effected in the samedirection (widthwise direction of the pressure chamber 10) as that ofthe first electric field E1 in the first zone 142, and the polarizationis effected in the same direction (longitudinal direction of thepressure chamber 10) as that of the second electric field E2 in thesecond zone 143. Therefore, the direction of polarization of thepiezoelectric layer 42 is the same as the direction of the electricfield generated when the voltage is applied to the individual electrode132.

In the piezoelectric actuator of the second modified embodiment, whenthe driving voltage is selectively applied to the plurality ofindividual electrodes 132 from the driver IC, the individual electrode132 and the common electrode 134 are allowed to have the mutuallydifferent electric potentials. Accordingly, as shown in FIG. 10, thefirst electric field E1, which is directed in the widthwise direction ofthe pressure chamber 10, is generated in the piezoelectric layer 42 ofthe first zone 142 in the inner area 140 of the piezoelectric layer 131disposed under or below the individual electrode 132 to which thedriving voltage is applied. Further, the second electric field E2, whichis directed in the longitudinal direction of the pressure chamber 10, isgenerated in the piezoelectric layer 42 of the second zone 143.

In this arrangement, as described above, the piezoelectric layer 42 ispolarized in the same direction as that of the first electric field E1in the first zone 142, and the piezoelectric layer 42 is polarized inthe same direction as that of the second electric field E2 in the secondzone 143. Therefore, as indicated by arrows in FIGS. 11 and 13, thepiezoelectric layer 42 is elongated in the widthwise direction of thepressure chamber 10 as the direction of the first electric field E1 inthe first zone 142, and the piezoelectric layer 42 is shrunk in thelongitudinal direction of the pressure chamber 10. On the other hand, inthe second zone 143, the piezoelectric layer 42 is elongated in thelongitudinal direction of the pressure chamber 10 as the direction ofthe second electric field E2, and the piezoelectric layer 42 is shrunkin the widthwise direction of the pressure chamber 10. That is, as shownin FIG. 13, as viewed in the widthwise direction of the pressure chamber10, the piezoelectric layer 42 is elongated in the first zone 142, andthe piezoelectric layer 42 is shrunk in the second zones 143 disposed onthe both sides thereof. In this situation, the vibration plate 41, whichis positioned under or below the piezoelectric layer 42 of the innerarea 140, makes no expansion/contraction in the in-plane direction, andthe vibration plate 41 resists the expansion/contraction deformation ofthe piezoelectric layer 42 of the inner area 140 in the in-planedirection. Further, the piezoelectric layer 42 of the outer area 141 tosurround the inner area 140 and the vibration plate 41 disposedthereunder are regulated or restricted for the deformation in thethickness direction. Therefore, as indicated by broken lines in FIGS. 12and 13, the piezoelectric layer 42 and the vibration plate 41 aregreatly curved and deformed so that they protrude in the upwarddirection (toward the side opposite to the pressure chamber 10). Whenthe vibration plate 41 is curved as described above, then the volume ofthe pressure chamber 10 is increased, the negative pressure wave isgenerated in the pressure chamber 10, and the ink is allowed to inflowinto the pressure chamber 10 from the manifold channel 13.

After that, the application of the driving voltage to the individualelectrode 132 is stopped at the timing at which the negative pressurewave generated in the pressure chamber 10 is inverted into the positive.Accordingly, the piezoelectric layer 42 and the vibration plate 41 arereturned to have the original horizontal shapes, and the volume of thepressure chamber 10 is decreased. However, in this situation, thepressure wave which is brought about by the increase in the volume ofthe pressure chamber 10 as described above and the pressure wave whichis generated by the restoration of the vibration plate 41 are combinedwith each other. Therefore, the large pressure is applied to the ink,and the ink is discharged from the nozzle 15.

When the ink-jet head (piezoelectric actuator) of the second modifiedembodiment is produced, then the vibration layer 41 is formed as thefilm on the upper surface of the cavity plate 21, and then thepiezoelectric layer 42 is immediately formed as the film on the uppersurface of the vibration layer 41. The individual electrodes 132 and thecommon electrode 134 are formed in the step of forming the individualelectrodes 44 in the embodiment of the present invention. The otherproduction steps are the same as or equivalent to those of theembodiment described above, any detailed explanation of which is omittedherein.

When the ink-jet head is produced as described above in the secondmodified embodiment, it is also possible to obtain the effect which isthe same as or equivalent to that obtained in the embodiment describedabove.

In the embodiment of the present invention, the pressure chambers 10 areformed for the cavity plate 21 by means of the etching. However, thepressure chambers 10 may be formed by means of any other methodincluding, for example, the laser processing. In this case, a plate madeof ceramics can be also used as the cavity plate 21. For example, thevibration layer may be formed by stacking another ceramics layer, forexample, by means of the AD method on an upper surface of the ceramicsplate having a predetermined thickness (˜20 μm). In this procedure, thethrough-holes, which serve as the pressure chambers, can be formed forthe cavity plate, for example, by means of the laser processing. Thecavity plate and the vibration layer may be formed of the same ceramicsmaterial. However, in view of the processability, it is desirable thatthe cavity plate can be easily subjected to the laser processing ascompared with the vibration layer. Even when the ceramics material ofthe cavity plate contains a large amount of impurities such as metalsand silicon, the harmful influence exerted on the piezoelectricperformance of the piezoelectric layer is mitigated in the same manneras in the embodiment described above, which would be otherwise caused bythe diffusion of the impurities such as metals and silicon when thepiezoelectric layer is annealed.

The foregoing description is illustrative of the exemplary case in whichthe present invention is applied to the production of the ink-jet headfor discharging the inks from the nozzles in the pressure chambers andthe piezoelectric actuator to be used therefor. However, the presentinvention is not limited thereto. For example, the present invention isalso applicable to the production of a liquid discharge head fordischarging any liquid other then the ink from the nozzle and apiezoelectric actuator to be used therefor. The present invention isalso applicable to the production of a liquid transport apparatus fortransporting any liquid in a liquid transport channel including apressure chamber by applying the pressure to the liquid contained in thepressure chamber, and a piezoelectric actuator to be used therefor.

Further, the present invention is also applicable to the production of apiezoelectric actuator for driving a predetermined driving objective. Inthis case, the driving objective may be attached to the portion of thelower surface of the vibration layer 41 exposed to the through-holeformed for the base member.

1. A method for producing a liquid transport apparatus that includes: apressure chamber plate including a pressure chamber that communicateswith a nozzle for ejecting liquid; a ceramics layer located on a surfaceof the pressure chamber plate to cover the pressure chamber; apiezoelectric layer located on the ceramics layer; and an electrodelocated on the piezoelectric layer; and wherein the method comprises:forming the ceramics layer on the pressure chamber plate at atemperature lower than an annealing temperature of the piezoelectriclayer; forming the piezoelectric layer and the electrode on the ceramicslayer; and forming the pressure chamber by removing a part of thepressure chamber plate.
 2. The method for producing the piezoelectricactuator according to claim 1, wherein the piezoelectric layer is formedby an aerosol deposition method.
 3. The method for producing thepiezoelectric actuator according to claim 1, wherein the ceramics layeris formed by an aerosol deposition method.
 4. The method for producingthe piezoelectric actuator according to claim 1, wherein the ceramiclayer is formed of zirconia.
 5. A method for producing a liquidtransport apparatus that includes: a pressure chamber plate including apressure chamber that communicates with a nozzle for ejecting liquid; aceramics layer located on the pressure chamber plate to cover thepressure chamber; a piezoelectric layer locate on the ceramics layer;and an electrode located on the piezoelectric layer; and wherein themethod comprises: forming the ceramics layer on the pressure chamberplate at a room temperature; forming the piezoelectric layer and theelectrode on the ceramics layer; and forming the pressure chamber byremoving a part of the pressure chamber plate.
 6. The method forproducing the liquid transport apparatus according to claim 5, whereinthe piezoelectric layer is formed by an aerosol deposition method. 7.The method for producing the liquid transport apparatus according toclaim 5, wherein the ceramics layer is formed by an aerosol depositionmethod.
 8. The method for producing the liquid transport apparatusaccording to claim 5, wherein the ceramics layer is formed of zirconia.9. A method for producing a liquid transport apparatus that includes: apressure chamber plate including a pressure chamber that communicateswith a nozzle for ejecting liquid; a ceramics layer located on thepressure chamber plate to cover the pressure chamber; a piezoelectriclayer located on the ceramics layer; and an electrode located on thepiezoelectric layer; and wherein the method comprising: forming theceramics layer on the pressure chamber plate at a temperature lower than850° C.; forming the piezoelectric layer and the electrode on theceramics layer; and forming the pressure chamber by removing a part ofthe pressure chamber plate.
 10. The method for producing the liquidtransport apparatus according to claim 9, wherein the piezoelectriclayer is formed by an aerosol deposition method.
 11. The method forproducing the liquid transport apparatus according to claim 9, whereinthe ceramics layer is formed by an aerosol deposition method.
 12. Themethod for producing the liquid transport apparatus according to claim9, wherein the ceramics layer is formed of zirconia.